Developers using the hosting service who want to go beyond App Engine's free quota limits will be able to pay for more resource usage

Google on Tuesday will institute new billing services for developers using its App Engine hosting service for Web applications, but developers will be able to go beyond the capacity quotas that had been in place, a Google product manager said.

Until now, App Engine storage has been free but developers could only access around 40 hours of CPU time per day along with 500MB of storage and 10GB of bandwidth, said Pete Koomen, product manager for Google App Engine.

"What we're enabling [Tuesday] is for developers who want to go beyond these limits, we're now giving them the ability to pay for more resource usage," Koomen said. On top of the free services, developers can pay 10 cents per CPU core hour for application processing, 10 cents per gigabyte of data transferred into the application, 12 cents per gigabyte of data transferred out of the application, and 15 cents per gigabyte per month of storage. The storage capabilities cover static files served by the application as well as structured data using the Google Datastore API.

In addition to the 2,000 e-mails a day that applications can send for free, Google will let applications send 10,000 e-mails per day for $1.

"[The effort is] a way to allow developers to grow beyond the free quotas," Koomen said.

"App Engine will always be free to get started," the company stated in a planned blog post. "However, we've made many performance improvements over the past 10 months and we've also learned that we were pretty conservative with our initial estimates on what our free resource quotas should be. Therefore, in 90 days we will be reducing the free quota resources. We believe these new levels will continue to serve a reasonably efficient application around 5 million page views per month, completely free."

The company, however, will double its free storage quota.

"Data stored in the datastore incurs additional overhead, depending on the number of indexes, as well as the number (and size) of associated properties," Google said. "This overhead can be significant in some cases and it's something that we've been underreporting to date. So you may notice adjustments in the amount of data stored that's listed in the Admin Console. To decrease the impact of these adjustments, we've doubled the free storage quota to 1GB," the company said.

An estimated 45,000 applications have been built on App Engine, Koomen said. Among these applications are BuddyPoke, which is an OpenSocial application with more than 30 million users, and Lingospot, for content discovery.